Production of mixed shrinkage polyester yarn

ABSTRACT

Mixed-shrinkage, continuous-filament, heat-bulkable yarn, composed of low and higher shrinking filaments of different polyester compositions, develops worsted-like bulk in fabric as a result of normal fabric-finishing operations. The yarn is prepared from two ethylene terephthalate polyesters, of different compositions and relative viscosities, by cospinning, drawing and heat-setting the filaments under identical, critically-controlled conditions.

United States Patent [191 Reese Dec. 16, 1975 PRODUCTION OF MIXEDSHRINKAGE [56] References Cited POLYESTER YARN UNITED STATES PATENTS[75] Inventor: Cecil E. Reese, Kinston, NC. 3,593,513 7/1971 Reese57/140 Assigneez E. L Du Pont de mo s and 3,705,225 12/1972 Taylor264/210 F Company wllmmgton Primary Examiner-Jay H. W00 [22] Filed:Sept. 26, 1972 21 Appl. No.2 292,300 [57] ABSTRACT Mixed-shrinkage,continuous-filament, heat-bulkable [44] g g i gg g ggfii g fg g gl gg gf yarn, composed of low and higher shrinking filaments B 3 300 Ty en ofdifferent polyester compositions, develops worstedlike bulk in fabric asa result of normal fabric-finishing operations. The yarn is preparedfrom two ethylene [52] Cl 264/210 57/140 g i terephthalate polyesters,of different compositions and [51] Int C12 D011) 5/12 relativeviscosities, by cospinning, drawing and heat- [58] Fieid s 03 290 Tsetting the filaments under identical, criticall 264/210 controlledconditions.

4 Claims, N0 Drawings PRODUCTION OF MIXED SHRINKAGE POLYESTER YARNBACKGROUND OF THE INVENTION This invention relates to bulkable polyestertextile yarns, and more particularly to mixed-shrinkage yarn composed ofan intimate mixture of polyester filaments of more than one type.

Uncrimped polyester yarns of straight continuous filaments areundesirable-in most fabrics because they provide a non-bulky, slickhand. Various texturing methods have been devised for crimping thefilaments to provide bulk. Bulk can also be produced by making the yarnof a mixture of filaments, some of which shrink more than others whenheated. Such mixed-shrinkage yarns can be bulked by heating prior toweaving, but is it most advantageous to develop the bulk after weavingby heating during normal fabric finishing operations.

Mixed-shrinkage polyester yarns have been prepared by plying filamentsproduced under different conditions. Maerov et al. US. Pat. No.3,200,576 discloses simultaneous melt-spinning of two plies, with oneply being annealed after drawing to provide from 2 percent to 20 percentdifference in boil-off shrinkage relative to the other ply. Heating themixed-shrinkage yarn causes the higher shrinking filaments to pull theother filaments into a bulky configuration, but the patent disclosesthat non-uniformity in bulkiness occurs to follow-the-leader looping offilaments and causes objectionable moire in fabric (undesirablepatterning) unless the filaments are properly intermingled. Maerov eta1. teach jet interlacing the filaments to a split count of less than 12inches (preferably 1 to 3 inches) to overcome this problem.

Reese US. Pat. No. 3,593,513 is concerned with improving the appearanceof fabric when yarn filaments differ in color or luster, and disclosesthat formation of an objectionable moire due to heterogeneous yarn canbe avoided if the filaments are spun simultaneously and brought togetherfor intermingling prior to drawing. A uniform, pleasant heather wasobtained in dyed fabric when filaments having different affinity for dyewere cospun from different orifices of the same spinneret and thereafterprocessed in combination. A test for determining the degree of filamentintermingling (DFI) is described. The patent teaches that the DFI shouldbe between 80 percent and 100 percent for best results. The patent showsthat this DFI was achieved when plies of as-spun filaments were combinedinto a yarn, intermingled during drawing, and then interlaced. Theinterlacing step was not needed when the filaments were cospun from thesame spinneret and drawn as a composite yarn.

Reese US. Pat. No. 3,444,681 discloses preparation of a mixed-shrinkagepolyester yarn by a process in which two species of filaments having thesame chemical composition and different relative viscosity (RV) areseparately spun, the higher RV filaments are spinannealed, and thefilaments are then combined for drawing and subsequent processing. Thefilaments may be composed of polyethylene terephthalate, where onespecies has an RV of 15 to 30 and the other species has an RV at least 8units higher. Adequate filament intermingling can be achieved in theprocess, but the requirement for different spin-anneal conditionsprecludes cospinning the higher RV species for the same spinneret as theother species. Cospinning would be highly desiraable for economicreasons and because it provides better filament intermingling.Furthermore, it is frequently desirable to prepare mixed-shrinkagepolyester yarns of filaments having different affinities for dyes inorder to provide a uniform, attractive heather appearance in dyedfabric.

The filaments of a yarn must be drawn to at least the natural drawratio, since less complete drawing results in undrawn segments whichcause uneven dyeing and harsh tactility in fabric. For uniform drawingof a composite yarn, the filaments must have approximately the samenatural draw ratio and also draw to nearly the same break elongation (nogreater than 15 percent difference) in order to avoid broken filamentsand segments which are weak or cause unevenly dyes filaments. US. Pat.No. 3,444,681 teaches that this is accomplished by critical adjustmentof the spinannealing conditions. The yarn is also heat-treated at 135 to165C. after drawing to provide a low boil-off shrinkage so that most ofthe bulk will develop at higher te mperatures when fabric is heat-set innormal finishing operations. Greater bulk is obtained by increasing thedifference in molecular weight (which is indicated by RV) between thetwo species.

SUMMARY OF THE INVENTION The present invention provides an improvementin the process for producing mixed-shrinkage polyester yarn whereby thelow-shrinkage and higher-shrinkage filaments are spun and processedunder identical conditions. The invention further provides forcospinning the filaments from a single spinneret and thereafterprocessing the filaments as a single yarn so that a high degree offilament intermingling is achieved. Furthermore, the higher shrinkagefilaments have a chemical composition which is different from that ofthe lowshrinkage filaments and can be varied to provide the same ordifferent affinity for dyes. The invention provides an improvedmixed-shrinkage yarn which imparts to fabrics produced therefrom ahighly desirable worsted-like bulk and tactility. The yarn is free fromundesirable loops after take-off from yarn packages and is suitable forweaving before bulking, followed by dev elopment of the bulk duringnormal fabric finishing op erations. The filament compositions can bevaried to provide uniform dyeing or pleasant heather effects. A highdegree of filament intermingling provides freedom from moire in fabric.

In the preferred process of the present invention, low-shrinkagefilaments and higher-shrinkage filaments of different chemicalcomposition are prepared sirn ultaneously under identical conditions bycospinning the different polyester compositions from separate orificesof the same spinneret, quenching the filaments and combining them into ayarn, drawing the yarn in to C. water to at least the natural draw ratioof the filaments, and heat-setting the yarn at a temperature within therange of about to C. to produce a yarn characterized by low-shrinkagefilaments of polyester having a relative viscosity of about 14 to 19 anda density of at least 1.3800, aand higher-shrinkage filaments having arelative viscosity between 27 and 40, a density of less than 1.3840, aboil-off shrinkage greater than 7.5 percent, and a break elongation ofwithin 15 percentage units of the low-shrinkage filaments. The yarn canalso be drawn while passing through a steam jet instead of drawing in 85to 100C. water. Super 3 heated steam at 200 to 270C. and 55 to 80 poundsper square inch gauge pressure is suitable for the steam jet. Steamdrawn yarn can be heat-set at a temperature as low as l 10C. to providethe indicated properties.

The low-shrinkage, low RV filaments are prepared from polyester wherein95 to 100 mole percent of the structural units are ethyleneterephthalate and the remaining 5 to mole percent of the structuralunits are ethylene S-(alkali metal sulfo)isophthalate. A preferredcopolyester has 98 mole percent ethylene terephthalate and 2 molepercent ethylene 5-.(sodium sulfo)isophthalate, abbreviated 2G-T/1S(98/2).

The higher-shrinkage, higher RV filaments are prepared from a polyesterof different chemical composition wherein 85 to 95 mole percent of thestructural units are ethylene terephthalate and the remainder are otherester units to retard crystallization of the copolyester relative to thehomopolyester of ethylene terephthalate. Any of the structural unitsknown to form useful copolyester filaments with ethylene terephthalatemay be used for the purpose. This use of a crystallization retardant inproper amount makes possible cospinning and processing the low andhigher shrinkage filaments under identical conditions to providemixedshrinkage yarn having the desirable properties indicated herein.

To avoid confusion in the meaning of the terms polymer, polyester,copolymer, copolyester, terpolymer, terpolyester, etc., as used herein,it should be understood that polymer or polyester are generic topolymers wherein one, two or more different structural units arepresent, copolymer or copolyester mean that two or more are present, andterpolymer or terpolyester mean at least three. The relative viscositiesare measured on filaments after spinning, drawing and heat-set ting at130 to 160C. unless otherwise specified. The polymer before spinningmust have a slightly higher relative viscosity to compensate fordegradation which takes place during the melt-spinning operation.

The mixed-shrinkage yarn of the present invention is characterized bylow-shrinkage and higher-shrinkage filaments have a degree of filamentintermingling between 80 and 100 percent when measured as described inU.S. Pat. No. 3,593,513. The low-shrinkage filaments consist ofpolyester having a relative viscosity of 14 to 19, a density of at least1.3800, and wherein 95 to 100 mole percent of the polymer structuralunits are ethylene terephthalate and the remaining 5 to 0 mole percentof structural units are ethylene 5-(alkali metal sulfo)isophthalate. Thehigher-shrinkage filaments consist of a different polyester having arelative viscosity greater than 27, a density of less than 1.3840, aboiloff shrinkage greater than 7.5 percent, a break elongation within 15percentage units of the low-shrinkage filaments, and wherein 85 to 95mole percent of the structural units are ethylene terephthalate and theremainder are crystallization retardant units forming a copolyestertherewith. The yarn provides a differential filament length value (DFL)of 3.5 percent to percent when tested under simulated fabric finishingconditions as described subsequently.

One preferred embodiment of the invention is a mixed-shrinkage yarnwherein 25 to 75 percent of the filaments are low shrinkage filaments of2G-T/1S polyester having an RV of about and a density of about 1.3834,and the other filaments are higher shrinkage filaments of a copolyesterof ethylene terephthalate and ethylene isophthalate (2G-T/I) having anRV of 4 about 35 and a density of about 1.3660. This yarn providesexcellent bulk when fabric containing it is subjected to normalfinishing operations, dyes uniformly in disperse dye baths, and can becross-dyed to provide desirable heather effects, since only the 2G-T/ISfilaments are receptive to cationic dyes.

Another preferred embodiment is one in which the low-shrinkage filmentsare 2G-T/IS polyester having an RV of about 15 and a density of about1.3834, and the higher-shrinkage filaments are 2G-T/6 copolyester(ethylene terephthalate and ethylene adipate structural units) having anRV of about 35 and a density of about 1.3668.

DETAILED DISCLOSURE The low-shrinkage 2G-T filaments may be prepared byany of a variety of procedures known in the art, such as by one of themethods taught by Whinfield and Dickson in U.S. Pat. No. 2,463,319. Itwill be apparent to those skilled in the art that the low-shrinkagecomponent of the new yarns has an unusually low RV; i.e., from about 14to 19. If 2G-T/IS is used for the lowshrinkage filaments, it may beprepared by one of the methods of Griffing and Remington described inU.S. Pat. No. 3,018,272. The mole ratio of S-(sodium sulfo)isophthalateunits to terephthalate units is less than 5:95.

It was totally unexpected that 2G-T or 2G-T/IS could be spun and drawnat the same temperature and draw ratios to produce the same or nearlythe same break elongations as a different ethylene terephthalatecopolymer to produce a mixed-shrinkage yarn having not only suchdesirable differential filament length properties, but other aestheticqualities sought after in commerce.

The polymer to be used as the high-shrinkage filamentary member of thenew yarn may be produced by known techniques for preparing thecopolyester, bearing in mind that the relative viscosity should begreater than 27. Generally, it is made by charging into a distillationcolumn the dimethyl esters of the appropriate acids, such asdimethylterephthalate and dimethylisophthalate in the required moleratio. Approximately 2.2 moles of ethylene glycol or other suitable diolare added for each mole of diester. Manganese acetate and antimony oxideare added in catalytic amounts. The temperature is raised, methanoldistills off, and the bisglycol of the ester is formed until thetemperature of the still reaches about 240C., at which temperaturesubstantially all the methanol hasevolved. The batch is then droppedinto an autoclave equipped with a stirrer, the pressure is decreased,and the temperature is slowly increased to remove excess glycol andbegin polymerization. The temperature is raised to 270C. When thedesired RV is attained, the polymer is extruded as a ribbon over a coolmoving surface and chopped into flake in a conventional manner.

A large number of ethylene terephthalate copolyesters are known toprovide useful filaments and can be used for the present invention. Theglycol and/or the acid can be varied, or caprolactone can also be usedto provide structural units in the copolyester chain of thehighershrinkage filaments. Illustrative of structural units which may beused as crystallization retardants in the polyester chain are fromethylene glycol and isophthalic acid,

II ll from 2,2-dimethyl-trimethylene glycol and terephthalic acid,

0 0 II II -ca cn -o-c-( c11 -c-ofrom ethylene glycol and dodecanediocacid,

from ethylene glycol and hexahydroterephthalic acid, and others of thesame class represented by the general formula 0 0 II II (A-O) -CB-C-O-'wherein A is a lower alkylene group, n is l, 2 or 3, and B is a divalenthydrocarbon group having up to carbon atoms in the polyester chain andis free from aliphatic unsaturation.

The new yarns contain from about 25 percent to about 75 percent of eachtype of filament. Preferably, they contain about 50 percent oflow-shrinkage filaments and about 50 percent of high-shrinkagefilaments. The yarns may be of any conventional denier and contain anynumber of filaments greater than 2. Preferably, the denier per filamentof the filaments in the new yarns is substantially uniform and between iand 5. Yarn deniers are preferably at the commercial levels.

The break elongation of the constituent fibers of the new yarn must bewithin about 15 percent units of each other. If the break elongations ofthe filaments vary outside this range, problems such as broken filamentsand undrawn segments. of yarn which cause dye nonui 6 niformities orweak spots along the filament length occur.

It is important that the relative viscosity of each group of filamentsof the new yarns be within the specified ranges. If the RV of thehigh-shrinkage filamentary component of the new yarns is greater thanabout 40, it will be difficult to select a suitable common draw ratio.If the RV of the high-shrinkage filamentary component is less than thespecified lower limit, its draw ratio will be too high and the DFL willbe below the lower limit specified for a satisfactory product. If the RVof the low-shrinkage filamentary component is more than the specifiedupper limit, its shrinkage is too high and the DFL is unacceptably low.If the RV of the low-shrinkage filamentary component is less than aboutthe specified lower limit, fabrics produced from the yarn areunacceptable because they are prone to abrasion damage which is causedby the ease of breaking of the lowshrinkage filamentary component.

The yarns of the present invention are, in general, produced byconventional melt-spinning techniques. Preferably, they are produced bycospinning both polymeric species through a single spinneret, onespecies extruding through some of the orifices of the spinneret and theother species through the other orifices. Methods for doing this areknown in the art as disclosed, for example, in Reese US. Pat. No.3,593,513. The new yarns may be spun and drawn as an integral yarn andthereafter heat-set and wound up onto a suitable package.

The fact that the new yarns may be produced by cospinning and codrawingpresents an economic advantage because separate equipment is notrequired to process each filament species. Also, because the yarns maybe cospun and codrawn, the filament species are well intermingled,producing a uniform visual appearance in fabrics made therefrom.

The new yarn has the advantage that the desirable bulk and tactileaesthetics can be developed in the normal sequence of finishingoperations; namely, scour at the boil and fabric heat-setting underconventional conditions. No special treatments are required.

In order to produce the yarns of the present invention, these filamentsmust be heat-set in their manufacture to allow the low-shrinkagefilaments to reach a density of at least 1.3800.

This is preferably carried out by passing the yarn over draw rolls whichare heated to a temperature within the range of about to C. and usuallyabout 150C. When using certain polymers as the high-shrinkage component,such as poly(ethylene terephthalate/dodecanedioate) (90/ 10), draw rolltemperatures as high as C. may be used without adversely affecting thedifferential filament length property. Yarn exposure to the heated rollsshould be from about 1 to 0.001- second.

The invention will be further illustrated by the following examples ofembodiments which are not intended'to be limitative.

DEFINITIONS Differential Filament Length (DFL). The yarn to be tested iswound on a reel the number of times required to achieve a loop denier of3,000 using the formula:

n l500/D wherein n is the number of turns and D is the denier of theyarn. Obviously, the loop denier increases 2D for each n. The loop isremoved from the reel and immersed in boiling water for minutes. Theloop is then transferred to a second boiling aqueous bath which containsgrams of Latyl Carrier A in 2 liters of water. Latyl Carrier A is thetradename for a dye assistant for improving the dye-ability of polyesterfibers and which is sold commercially by E.l. du Pont de Nemours andCompany. It is a mixture of about 0.2 percent sodium lauryl sulfate,about percent sodium sulfate, about 40 percent benzanilide, and about 40percent dimethylterephthalate. After 1 hour, the loop is removed fromthe bath and then placed on a frame and tensioned slightly, just enoughto straighten the shortest constituent loops. The frame bearing the loopis placed in an oven at 160C. dry heat. After seconds exposure, the loopis removed from the oven, removed from the frame and 150 gram weight issuspended from it and its length is measured (L The weight is removedand the loop is then stretched until the longest constituent loops arejust straightened. In this condition, the high-shrinkage andlow-shrinkage components of the loop are approximately of the samelength. The length of the skein is then measured (L DFL is measured bythe following formula:

It will be appreciated that in this measurement the yarn is treated muchlike it would be treated in a commercial fabric-manufacturing operationand DFL determines the suitability of a bulk yarn for a textile fabric.This method is used in Examples 1, II and Ill herein.

A short-cut method for approximating differential filament length is asfollows:

The high-shrinkage component of the yarn to be tested is wound on a reelas shown above. The loop is removed from the reel, a 26.4 gm. weight issuspended therefrom, and its length measured (L The weight is removedand the loop is then suspended in boiling water, at 100C., for 1 hour.The loop is then removed from the water, the weight is again suspendedtherefrom, and its length measured (L The low-shrinkage component of theyarn to be testedis then treated in the same manner, its original lengthbeing recorded as L instead of L except that instead of being suspendedin boiling water, the loop is suspended in an oven set at 160C. After30-seconds exposure, the loop is removed from the oven, allowed to cool,the 26.4 gm. weight is again suspended therefrom, and the length of theloop is measured (L Approximate DFL is obtained by the followingformula:

(Approximate) DFL(%) BOS DHS(%) wherein BOS(%) 100(L L )/L and DHS(%)G412 LH)/L02 Fabric bulk has been found to be a function of theshrinkage in boiling water of the high-shrinkage component minus thedry-heat shrinkage of the low-shrinkage component. Heretofore, thisrelationship was not clearly defined. It is evident that the method forapproximating DFL may be used to show the suitability of varioushigh-shrinkage and low-shrinkage components for the invention withouthaving to combine them to a yarn. This method is used in Example IV ofthis specification. I

The new yarns have differential filament length values, measuredaccording to either or both of the above methods, within the range ofabout 3.5 percent to 10 percent and preferably 6 to 8 percent. Theimproved 8 properties characteristic of this invention have not beenobtained in fabrics produced from previous yarns having DFL valuesoutside of this range.

Relative Viscosity (RV) of the polyester is a measure of its molecularweight. RV is the ratio of the viscosity of a solution of 2.15 grams ofpolymer dissolved at 140C. in 20 ml. of fomal to the viscosity of thefomal itself, both measured at 25C. in a capillary viscometer andexpressed in the same units. Fomal is a mixture of 10 parts by weight ofphenol and 7 parts by weight of 2,4,6-trichlorophenol.

Break Elongation is measured according to the ASTM designation D-2256-69(incorporating editorial edition of Section 2 and renumbering ofsubsequent sections as done in March 1971). It is defined as in Option3.3 Elongation at Break of Section 3. The testing is performed onstraight multifilament yarns which were conditioned by storing them at65 percent relative humidity and 70F. (21 .1C.) for 24 hours prior totesting. An Instron Tensile Testing Machine is used. The test sample is5 inches (12.7 cm.) long, no twist is added, the cross-head speed is 10inches per minute (25.4 cm./min.), the rate of attenuation is 200percent per minute, and the chart speed is 5' inches per minute (12.7cm./min.).

EXAMPLE I This example shows the importance of controlling the relativeviscosity (RV) or each filamentary component in the practice of thepresent invention.

A. RV of each component is in accordance with the teachings herein: v

2G-T/IS (92/2) flake as described in Griffing & Remington U.S. Pat. No.3,018,272 of 16 RV and 2G- T/I (/10) flake of 40 RV are separatelymelted and cospun to a 70-denier/28-filament composite yarn bydelivering equal volumes of each polymer melt to a spinneret containingorifices of uniform size arranged in concentric rings with an equalnumber of orifices in each .ring. The two polymer melts are preventedfrom mixing. The 2G-T/IS copolymer is spun through the outer ring andthe other copolymer is spun through the inner ring.

Spinning temperature, measured at the spinneret,

is 300C. The filaments are air-quenched in normal fashion and drawn 4.5Xby passing in contact with a draw pin situated between a feed roll and aset of two heated draw rolls. The draw pin is partially immersed in 95C.water. The filaments are wrapped 16 times around the two draw rolls,which are heated to C. The filaments are then given a coating of astandard finish and are passed to a suitable windup. Windup speed isabout 2,700 yards per minute (2,469 meters/minute). Break elongation ofeach filament group of the composite yarn is about 23 percent. The yarnhas a tenacity of 3.48 grams per denier. The 2G-T/IS filaments havearelative viscosity (RV) of 14.9 and a density of greater than 1.3830,while the ZG-T/l filaments have an RV of 38 and a density of less than1.3830. The differential filament length is found to be 5.5 percent. Theyarn forms no undesirable loops when removed from the package. Fabricwoven from the yarn and finished in normal manner has a worstedlikehand.

B. RV of the low-shrinkage component is too high:

Part A of this example is repeated with the exception that the RV of the2G-T/IS filaments is greater than 9 22, the break elongation differencein the two species of filaments is greater than percent units, andfabrics woven from this yarn lack bulk and have poor tactile aesthetics.

C. RV of the low-shrinkage filamentary component is too low:

Part A of this example is repeated with the exception that the RV of the2G-T/lS flake is 13 and the RV of the 2G-T/l flake is 40, the draw ratiois 4.8x. The RV of the 2G-T/IS filaments is 13.4 and the RV of the2G-T/l filaments is 34. The tenacity of the yarn is 3.19 grams perdenier, and the break elongation of both species of filaments is 21.6percent. The DFL of this yarn if 6.4 percent. A 7 oz. per yd. (237.4gm./meter 2 X 2 twillherringbone greige fabric is maade from this yarnusing 58 ends per inch (22.8 ends/cm.) for the warp and 56 picks perinch (22.0 picks/cm.) for the filling. After testing the fabric for theeffects of abrasion by a standard test, the fabric is found to beunacceptable because it is damaged severely by abrasion. The damage isfound to be caused by breaking of the lowshrinkage filamentarycomponent.

D. RV of the high-shrinkage component is too low:

Part A of this example is repeated with the exception that thehigh-shrinkage component is poly(ethylene terephthalate/adipate) (92/8), abbreviated 2G-T/ 6, the RV of the 2G-T/ 6 flake is 27.5, and the RVof the 2G -T/1S flake is 16. The RV of the 2G- T/6 filaments is 25.4 andthe RV of the 2G-T/IS filaments' is 15.4. The temperature of the drawrolls has to be reduced to 120C. in order to produce any differentiallength change whatever in the filame'ntsDFL of this yarn is found to beonly 3.5 percent.

EXAMPLE 11 This example shows the criticality ofthe annealingtemperature in the practice of this invention.

Part A of Example 1 is repeated with the exception that the draw rolltemperature is 180C. instead of 140C. Broken filaments are numerous andthe DFL of the resulting yarn is only 1 percent.

The example is repeated with the exception that the draw rolltemperature is 170C. The DFL of this yarn is only 2.4 percent.

The example is repeated with the exception that the draw rolltemperature is 155C. The resulting yarn has a DFL of 6.4 percent andforms no undesirable loops when removed from the package. Fabrics wovenfrom the yarn hag; worsted-like hands. They have unusual and highlydesirable bulk and texture, and fabrics woven therefrom have theaesthetics of worsted fabrics.

The example is repeated with the exception that the draw rolltemperature is only C. The density of the 2G-T/1S filaments is less than1.3800, and the fabrics woven therefrom have poor tactile aesthetics.

EXAMPLE III Part A of Example I is repeated, using 2G-T/6 (95/5) of 40RV (flake) as the high-shrinkage component and 2G-T/lS (98/2) of 16 RV(flake) as the low-shrinkage member. Draw ratio is 4.6X instead of 4.3and thedraw roll temperature is 134C. instead of C. The RV of the 2G-T/6 filaments is 33.1 and the RV of the 2G-T/lS filaments is 15.6.Density of the 2G-T/6 filaments is less than 1.3830. Density of the2G-T/IS filaments is greater than 1.3830. The DFL of this composite yarnis 7.1 percent, the tenacity is 4.65 grams per denier, and the breakelongation is 23 percent. Both components of the yarn have approximatelyequal break elongations. The yarn is of high quality. No loops occurwhen the yarn is withdrawn from the package. When the yarn is woven to afabric, the fabric has excellent bulk even after heat-setting, and has aworstedlike hand.

EXAMPLE IV This example shows the production of various copolymers andtheir suitability in the practice of the invention.

A series of polyesters, having 90 mole percent recurring structuralunitsrepresented by the formula:

. 0 o r A 11 II rollers. The draw rolls rotate at a peripheral speed ofabout 2,5 50 yardsper minute (2,332 meters/min), are heated to 140C. andthe yarns wrap around them as in the previous examples. The draw ratiosand deniers after drawing are indicated in the Table.

70ml: of diatom. :sructunl Unit Elorgation It RV Density Ben-0!! InkTenacity of or Shrinks for-n1. of Addition]. av Extrusion mm xv !Ieruitjnan-or? lmetunl mm: of. l'caplrlck react-t1 of o 9 g f= 1-s 29o 3.11:111 2a .4 30 1.3381 19 I o o II N I II I -cx ca 0-c@-c-o 1:2.0 .a9o 7o 2514.7 36 1.3600 in Bearing the foregoing teachings in mind, these dataindicate that each of the above copolyesters is suitable for cospinningwith either 2G-T or 2G-T/IS of an RV within the prescribed range,codrawing and heat-setting as specified to produce a mixed-shrinkageyarn of the present invention having a DFL within the range of about 3.8to 10 percent.

The present invention provides a new process for producing anall-polyester mixed-shrinkage yarn having excellent bulk andworsted-like aesthetics which involves treating the extruded filamentsas a single threadline from extrusion to windup. There is no necessityto split the process and thus costly equipment is avoided.

Fabrics prepared from yarns of the present invention 7 have unusual bulkand texture and possess the aesthetics of worsted fabrics. Thesequalities coupled with the inherent advantages of all-polyester fabrics,including moth and mildew resistance, make such fabrics highly desirablein todays market.

Fabrics produced from the new yarns may be made into slacks, coats,jackets, dresses, suits, and the like. Interesting dyeing effects can beobtained with fabrics made from the yarn of the present invention whichcomprises a mixture of 2G-T/IS fiber with another copolymer fiber suchas 2-G-T/l. The 2G-T/I fiber dyes easily with disperse dyes, but doesnot take up cationic dyes, whereas, the ZG-T/IS fiber takes up bothdisperse and cationic dyes.

I claim:

1. In the production of continuous-filament textile yarns, whereinpolyester filaments are melt-spun from spinneret orifices, quenched,combined into a yarn,

drawn to at least the natural draw ratio and heat-set, the improvementfor preparing mixed-shrinkage, heatbulkable yarn, wherein the improvedprocess comprises forming filaments having a relative viscosity of 14 to19 by melt-spinning a polyester, wherein 95 to 100 mole percent of therepeating structural units are ethylene terephthalate and 5 to 0 molepercent of the structural units are ethylene S-(alkali metal sulfo)-isophthalate, simultaneously forming filaments having a relativeviscosity between 27 and 40 by melt-spinning under the same conditions adifferent type of polyester of ethylene terephthalate which includesother ester units to retard crystallization of the polyester, from tomole percent of the polyester structural units being ethyleneterephthalate, quenching the 14 .to 19' and 27 to 40 relative viscosityfilaments under the same conditions and combining them into a yarn, thendrawing the yarn about 4X and heat-setting the yarn at a.

temperature within the range of 130 to 160C. to produce 14 to 19relative viscosity filaments having a density of at least 1.3800, and 27to 40 relative viscosity filaments having a density of less than 1,3840,a boil-off shrinkage greater than 7.5 percent and a break elongationwithin 15 percentage units of the 14 to 19 relative viscosity filaments.

2. A process as defined in claim 1, wherein the filaments are cospunfrom separate orifices 'of the same spinneret.

3. A process as defined in claim 1, wherein the yarn is drawn in 85 toC. water. g

4. A process as defined in claim 3, wherein the yarn is heat-set for lto 0.001-second on draw rolls heated to a temperature within the rangeof to C.

1. IN THE PRODUCTION OF CONTINOUS-FILAMENT TEXTILE YARNS, WHEREINPOLYESTER FILAMENTS ARE MELT-SPUN FROM SPINNERET ORIFICES, QUENCHES,COMBINED INTO A YARN, DRAWN TO AT LEAST THE NATURAL DRAW RATIO ANDHEAT-SET, THE IMPROVEMENT FOR PREPARING MIXED-SHRINKAGE, HEAT-BULKABLEYARN, WHEREIN THE IMPROVED PROCESS COMPRISES FORMING FILAMENTS HAVING ARELATIVE VISCOSITY OF 14 TO 19 BY MELT-SPINNING A POLYESTER, WHEREIN 95RO 100 MOLE PERCENT OF THE REPEATING STRUCTURAL UNITS ARE ETHYLENETEREPHTHALATE AND 5 TO 0 MOLE PERCENT OF THE STRUCTURAL UNITS AREETHYLENE 5-(ALKALI METAL SULFO)-ISOPHTHALATE, SIMULTANEOUSLY FORMINGFILAMENTS HAVING A RELATIVE VISCOSITY BETWEEN 27 AND 40 BY MELT-SPINNINGUNDER THE SAME CONDITIONS A DIFFERENT TYPE OF POLYESTER OF ETHYLENETEREPHTHALATE WHICH INCLUDES OTHER ESTER UNITS TO RETARD CRYSTALLIZATIONOF THE POLYESTER, FROM 85 TO 95 MOLE PERCENT OF THE POLYESTER STRUCTURALUNITS BEING ETHYLENE TEREPHTHALATE, QUENCHING THE 14 TO 19 AND 27 TO 40RELATIVE VISCOSITY FILAMENTS UNDER THE SAME CONDITIONS AND COMBININGTHEM INTO A YARN, THEN DRAWING THE YARN ABOUT 4X AND HEAT-SETTING THEYARN AT A TEMPERATURE WITHIN THE RANGE OF 130* TO 160*C. TO PRODUCE 14TO 19 RELATIVE VISCOSITY FILAMENTS HAVING A DENSITY OF AT LEAST 1.3800,AND 27 TO 40 RELATIVE VISCOSITY FILAMENTS HAVING A DENSITY OF LESS THAN1,3840 A BOIL-OFF SHRINKAGE GREATER THAN 7.5 PERCENT AND A BREAKELONGATION WITHIN 15 UNITS OF THE 14 AND 19 RELATIVE VISCOSITYFILAMENTS.
 2. A process as defined in claim 1, wherein the filaments arecospun from separate orifices of the same spiNneret.
 3. A process asdefined in claim 1, wherein the yarn is drawn in 85* to 100*C. water. 4.A process as defined in claim 3, wherein the yarn is heat-set for 1 to0.001-second on draw rolls heated to a temperature within the range of130* to 160*C.